WASHINGTON (AP) — Two conservative religious groups say they were also the subject of unusual scrutiny from the Internal Revenue Service.

The son of the Rev. Billy Graham as well as leaders of Z Street, a conservative Jewish organization, have said they believe they were pressed by the IRS for more information because they advocated for conservative causes.

In a letter Tuesday to President Barack Obama and Vice President Joe Biden, the Rev. Franklin Graham said charities built by his father may have received extra scrutiny from the IRS because they advocated against gay marriage and the elder Graham appeared in ads urging support for candidates who oppose abortion.

“I do not believe that the IRS audit of our two organizations last year is a coincidence — or justifiable,” Franklin Graham wrote. “I am bringing this to your attention because I believe that someone in the administration was targeting and attempting to intimidate us.

This is morally wrong and unethical — indeed, some would call it ‘un-American.’”

Franklin Graham said his Boone-based charity Samaritan’s Purse and the Billy Graham Evangelistic Association, which is based in Charlotte, received IRS notices last September that their 2010 activities would be reviewed.

In the letter to Obama and Biden, Graham noted that the evangelistic association named for his father waded into a North Carolina election by running full-page newspaper advertisements urging support for a state constitutional amendment banning gay marriage.

Both Franklin Graham and the 94-year-old Billy Graham supported Republican nominee Mitt Romney in last year’s presidential election. Billy Graham also appeared in national newspaper ads and newspaper ads in Ohio urging voters to back candidates who base their decisions on biblical principles, oppose gay marriage and abortion, and defend religious freedoms.

After the November election, Franklin Graham said, the two organizations received official notices that they continued to qualify for exemption from federal income taxes.

Members of Z Street, a group based in Merion Station, Pa., filed suit in 2010 after its application for tax-exempt status stalled. The group’s president, Lori Lowenthal Marcus, told Fox News that she believes her organization — it advocates a staunch, pro-Israel position — was scrutinized in a way similar to tea party groups that the IRS has now acknowledged were inappropriately targeted.

In its suit, Z Street says it was told by the IRS that it was “scrutinizing” groups connected with Israel and that its case was being referred to a special IRS unit. Z Street’s application for status as a tax-exempt, 501 (c) 3 organization has not yet been approved. A hearing on its suit is scheduled for July 2 in U.S. District Court in Washington.

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Lowenthal said she believes Z Street was targeted because of her group’s views on Israel.

“We knew that this is classic viewpoint discrimination,” she said.

Dean Patterson, a spokesman for the IRS, said he could not comment on either Z Street or Franklin Graham’s claims.